INSM1 and small cell lung carcinoma: Here, we propose a stratification of SCLC into two subgroups based on the expression of two genes, INSM1 and YAP1. Our working model, borrowing the terminology of Gazdar and Minna, is that INSM1 positive tumors represent the ‘classic’ every-day SCLC that is chemo-sensitive, whereas INSM1 negative tumors, which include YAP1 positive tumors, represents a ‘variant’ form of SCLC that is chemo-refractive.